1. Field of the Invention
The present invention disclosed in the specification relates to a method of fabricating a semiconductor device having a wiring electrode comprising aluminum or including aluminum as a major component.
2. Description of the Related Art
In recent years, a necessity of fabricating several millions of large amount of semiconductor devices on one chip or on the same substrate has been enhanced with high density integration of device elements. The problem in fabricating large amount of semiconductor devices is the fabrication yield and operational failure of semiconductor devices considerably lowers the fabrication yield. As one of major causes of operational failure of semiconductor devices, contact failure is pointed out.
Contact failure is an operational failure caused when connection failure occurs at a portion of electrically connecting a wiring electrode and a semiconductor device (hereafter, referred to as contact). Particularly, the contact failure poses a serious problem in view of enhanced necessity of making electrical connection via a slender perforation (contact hole) by the miniaturizing technology and the multi layer wiring technology.
The causes of contact failure are grossly classified into three. The first cause is that a conductive film forming a wiring electrode and a source/drain region (semiconductor film) or a lead out electrode (conductive film) are not brought into ohmic contact with each other. This is due to the fact that an insulating coating, for example, a metal oxide or the like is formed on a contact face.
The second cause is that the coverage of a conductive film forming a wiring electrode is poor and disconnection is caused in a contact hole. In this case, improvement must be achieved by film forming method or film forming condition of the wiring electrode.
Further, the third cause is disconnection of a wiring electrode caused by the sectional shape of a contact hole or the like. The sectional shape of a contact hole is strongly dependent on etching conditions of an insulating material (SiN, SiO2, organic resin film or the like) covered on the contact portion.
Particularly, contact failure due to the second or the third cause is actualized with a higher aspect ratio of a contact hole by miniaturizing a semiconductor device.
It is an object of the present invention disclosed in the specification to reduce operational failure of a semiconductor device caused by contact failure by resolving the above-described problem. Particularly, it is an object of the present invention to provide the technology of eliminating contact failure when a material comprising aluminum or including aluminum as a major component is used as a wiring electrode.
Further, it is an object of the present invention to provide the technology of realizing a semiconductor device or an electro-optic device having high long period reliability by improving reliability of contact. Further, it is an object thereof to promote the yield of the fabrication steps.
According to an aspect of the present invention, there is provided a method of fabricating a semiconductor device having a structure having a conductive material and an insulating film formed on the conductive material comprising at least a step of forming a contact hole on the insulating film and exposing the conductive material at a bottom thereof, a step of forming a wiring material comprising aluminum or including aluminum as a major component which is brought into electrical contact with the conductive material at least at the bottom of the contact hole, a step of forming a film including an element belonging to 12 through 15 groups as a major component on a surface of the wiring material, and a step of fluidizing the wiring material by a heating treatment wherein the heating treatment is carried out at a temperature of 400xc2x0 C. or lower in an atmosphere including hydrogen.
The present invention is constituted by the technology (referred to as reflow technology) improving the coverage in respect of a contact hole by lowering temperatures of fluidizing a wiring material by adding an element belonging to 12 through 15 groups to the wiring material comprising aluminum (Al) or including aluminum as a major component and fluidizing the wiring material by a heating treatment.
Further, the most significant characteristic resides in that the reflow step can be executed at temperatures of 450xc2x0 C. or lower, preferably 400xc2x0 C. or lower (representatively 350 through 400xc2x0 C.) by performing the heating treatment in an atmosphere including hydrogen. Also, the inventors predict that a reflow operation can be performed even at temperatures lower than 350xc2x0 C. by optimizing conditions.
The temperature of 350xc2x0 C. is a temperature that is frequently used in hydrogenation, which is recognized as a temperature preventing an aluminum wiring from causing hillocks. Further, the temperature of 400xc2x0 C. or lower is extremely important in reducing or preventing thermal deterioration of wirings formed on other layers or insulating films (for example, organic resin film).
Further, according to the constitution of the present invention, by constituting a structure sandwiching a conductive film of a titanium (Ti) film or the like between the conductive material and the material comprising aluminum or including aluminum as a major component, excellent ohmic contact can be secured.
Further, as the conductive material, material comprising aluminum or including aluminum as a major component (for example, material for forming wirings or the like) or a conductive semiconductor material (for example, semiconductor material for forming source/drain region of transistor) is representatively pointed out. Naturally, metals such as tantalum, tungsten and the like and titanium silicide and the like are also included in the conductive material.
Further, as an element belonging to 12 through 15 groups utilized as a catalyst in the reflow step, one or a plurality of elements selected from the group consisting of Germanium (Ge), Tin (Sn), Gallium (Ga), Lead (Pb), Zinc (Zn), Indium (In) and Antimony (Sb) are effective.